News About El Nino Events 09-NOV-09 en-us Pasadena CA (SPX) Oct 09, 2009 - Since May 2009, the tropical Pacific Ocean has switched from a cool pattern of ocean circulation known as La Nina to her warmer sibling, El Nino. This cyclical warming of the ocean waters in the central and eastern tropical Pacific generally occurs every three to seven years, and is linked with changes in the strength of the trade winds.]]>